1. Field of the Invention
The present invention relates generally to a fin-shaped structure forming process, and more specifically to a fin-shaped structure forming process that forms fin-shaped structures having different widths.
2. Description of the Prior Art
Field effect transistors are important electronic devices in the fabrication of integrated circuits, and as the size of the semiconductor devices becomes smaller and smaller, the fabrication of the transistors also has to improve and is constantly enhanced to fabricate transistors with smaller sizes and higher quality.
With the increasing miniaturization of the semiconductor devices, various multi-gate MOSFET devices have been developed. The multi-gate MOSFET is advantageous for the following reasons. First, the manufacturing processes of the multi-gate MOSFET devices can be integrated into the traditional logic device processes, and thus are more compatible. In addition, since the three-dimensional structure of the multi-gate MOSFET increases the overlapping area between the gate and the substrate, the channel region is controlled more effectively. This therefore reduces the drain-induced barrier lowering (DIBL) effect and the short channel effect. Moreover, the channel region is longer for the same gate length. Therefore, the current between the source and the drain is increased. More precisely, a multi-gate MOSFET device includes fin-shaped structures on a substrate for gates or shallow trench isolation structures (STI) to be covered thereon, so that the gates or shallow trench isolation structures and the fin-shaped structures have multi-interfaces for forming gate channels or shallow trench isolation structures, and the widths and the lengths of the muti-interfaces decide the widths and the lengths of the gate channels, thus fin-shaped structures with different widths may be needed to achieve different purposes of multi-gate MOSFETs.